Apparatus for detecting and locating radioactive biological markers

ABSTRACT

An apparatus for sensing and locating sources of ionizing radiation retained in a turnout in a body environment, including a hand-held probe and comprising a housing with a sensor circuit for outputting a response to interaction between the radiation and the sensor; a unit for processing signals from the sensor circuit; and an indicator responding to driving signals applied thereto by generating an audible or visual output. Said hand-held probe comprises at least one scintillating plastic optical fibre (2) connecting the sensing end to a light sensor (1).

The present invention relates to an apparatus for detecting and locatingradioactive biological markers. Such an apparatus is intended forfinding β and γ radiation emitted by the radioactive nuclei coupled tomolecules injected into the human body before a surgical operation.

In the prior art, European Patent No. 284,542 of the company NEOPROBECORPORATION is, in particular, known, relating to a detector and locatorfor the emission of low-energy radiation.

This document describes an apparatus for detecting and locatingradiation sources retained by a tumor in the environment of a bodyexhibiting a background radiation level, comprising a probe which can bemanipulated by hand and comprising a casing having an anterior portionextending to a window which can be placed in the vicinity of the source,and a portion which can be gripped by hand, extending from the anteriorportion.

The apparatus of the prior art furthermore comprises a detector circuitin the casing for producing induced charges in response to aninteraction of the radiation with this detector and for supplyingdetector signals corresponding to these charges, transmission means fortransmitting these detector signals, signal processing means and warningmeans which respond to drive signals by emitting an output signal whichis perceptible in an audible manner, in response to the drive signalswhich are applied to it.

The signal processing means comprise an energy-level analysis networkfor evaluating the detector signals with respect to the noise exhibitedby the apparatus and for producing pulse data output signalsrepresenting the radiation, excluding practically all the noise, rangeselection means for producing a range function value for the pulse dataoutput signals, this value representing the rate of the pulse dataoutput signals representing the background radiation level, and controlmeans which respond to the pulse data output signals by continuouslyproducing the rates of appearance of these signals, over predeterminedtime intervals, appearing successively, the duration of which isselected in order to allow rapid updating, and responding to eachdiscrete value of the produced rate and of the range function byproducing the drive signals which have a sound-generating frequency whenthe value of the appearance rate is greater than the range functionvalue, so that the audibly perceptible output signal can be varied, inresponse to said sound-generating frequency, while being a function ofthe appearance rates of the pulse data output signals lying above thebackground radiation level.

The active probe of such an apparatus is of considerable size, whichdoes not allow satisfactory use in all operational cases.

An image converter associated with a bundle of scintillating opticalfibers has also been proposed in the prior art (French Patent No.2,575,858).

As in the case of the previous apparatus, the large size does not allowoptimum clinical use in all operations.

The object of the present invention is to provide an apparatus fordetecting and locating the β and γ radiation emitted by a radioactivetracer, which apparatus is inexpensive and is compatible with use inregions which are difficult to access.

For this purpose, the invention more particularly relates to anapparatus for detecting and locating ionizing-radiation sources retainedby a tumor in the environment of a body, of the type comprising a probewhich can be manipulated by hand and includes a casing comprising adetector circuit capable of producing a response to an interaction ofthe radiation with this detector, means for processing the signalscoming from the detector circuit and warning means which respond todrive signals by emitting an audibly or visually perceptible outputsignal in response to the drive signals which are applied to it,characterized in that the manipulable probe comprises at least onescintillating plastic optical fiber connecting the detection end to aphotodetector.

The apparatus according to the invention is composed of a casingcontaining all the electronic signal processing circuits, thephotodetector and the power supply. This casing may be arranged at aposition relatively far from the operation area, in contrast to theapparatus of the prior art which integrated at least the photodetectorinto the probe. The surgeon manipulates a probe which consists of theend of a flexible jacket containing the optical fiber or fibersfulfilling a first function as a light guide and a second function ofconverting β and γ radiation into light pulses. This jacket is veryflexible and has a small diameter of a few millimeters, which allowsaccess at locations which are inaccessible to the apparatus of the priorart.

In addition, there is no electrical connection between the casing andthe part of the probe capable of coming into contact with the patient.As a result of this, the working safety of the apparatus according tothe invention is reinforced in comparison to the apparatuses of theprior art, in which the photomultiplier housed in the end of the proberequires a high-voltage supply. According to an advantageous embodiment,the casing comprises a photomultiplier tube and means for opticalcoupling of at least one scintillating optical fiber clad in an opaqueflexible jacket, the end of which constitutes said manipulable probe.

Preferably, the flexible opaque jacket is sterilizable and contains abundle of from 2 to 6 scintillating optical fibers having a diameter ofapproximately 1 millimeter.

According to one advantageous embodiment, a shutter is arranged betweenthe photomultiplier and the means for optical coupling of the bundle ofscintillating fibers.

This embodiment prevents saturation of the photomultiplier when changingthe probe.

According to a variant, the end of the scintillating plastic fiber issolidly attached to a functional exploration tool.

According to another variant, the end of the scintillating plastic fiberis solidly attached to a surgical tool.

According to another variant, a plurality of scintillating opticalfibers, insulated from one another, form a bundle connected to amultichannel photomultiplier. This embodiment makes it possible to carryout imaging of the radioactive region. The detection ends of the fibersare organized in a matrix of N×M detection points.

The invention will be better understood on reading the followingdescription, referring to the drawings in which:

FIG. 1 represents a sectional view of the detection part in theseparated position;

FIG. 2 represents a sectional view of the detection part in the workingposition;

FIG. 3 represents a diagrammatic view of the apparatus according to theinvention.

The detection part of the apparatus according to the invention comprisesa photomultiplier (1) which converts the light signal emitted by thescintillating optical fiber (2) into an electrical signal. Thephotomultiplier is, for example, a photomultiplier marketed by thecompany PHILIPS under the reference RTC XP191, with a working diameterof 14 millimeters, having a bialkaline rubium photocathode and 10amplification stages.

The scintillating fiber (2) is, for example, composed of a scintillatorformed by a single solute dissolved in a solvent. The solute is, by wayof example, 6-(4-biphenylyl)phenylbenzoxazole (PBBO). Its concentrationis 4·10⁻³ grams per gram of solvent, the latter being polystyrene (n₁=1.59). The core of the fiber is coated with a film of polymethylmethacrylate (PMMA n₂ =1.49). The thickness of the film is approximately3% of the diameter in the case of fibers having circular cross section,or approximately 2% of the width for fibers having square cross section.Such fibers are, in particular, marketed by the company KURABAY underthe references SCS-38 or SCSF-81.

The scintillating fibers are combined into a bundle of 4 fibers (2)surrounded by a protective jacket (3) made of an opaque plastic whichcan be sterilized under ethylene oxide atmosphere at 55° C., for examplethe material marketed under the brand name ISOVERSINIC, having athickness of one millimeter.

The front end (4) of the Bundle of fibers (2) is closed by a plug (5)made of a material identical to that forming the jacket (3). The totallength of the fiber is approximately two meters.

In order to prevent dazzling the photomultiplier tube (1) when replacingthe scintillating fiber, this tube is housed in a tubular part (6) whoseinternal surfaces are covered with an absorbent coating, for example amatt black paint. The tubular part (6) has at its end a connectionadaptor (7) complementary with a plug (8) solidly attached to the end(9) of the fiber (3).

The plug (8) is housed, as represented in FIG. 2, on the adaptor (7) ofthe tubular part (6) in order to provide leaktight connection of thefiber (2) onto the casing. The tubular part (6) optionally includes ashutter 6a optically isolating the photomultiplier (1) from the outsidelight when the fiber (2) is not connected onto the adaptor (7).

FIG. 3 represents a diagrammatic view of the whole of the apparatusaccording to the invention.

It includes a high-voltage generator (11) delivering a photomultipliersupply voltage lying between 1000 volts and 1800 volts.

The signal coming from the photomultiplier (1) is processed by adiscriminator (12) which makes a comparison with a reference voltage,adjustable between 20 and 120 millivolts, in the example described. Thesignal thus processed is transmitted to a counting circuit (13) andfurthermore controls a sound generator (14) causing a sound signal atthe detection of each pulse. This generator allows the user to find thetarget emitting ionizing radiation audibly, without losing view of theoperation area.

The end of the scintillating fiber bundle (2) may be solidly attached toa functional exploration tool (10) as schematically shown in FIGS. 1 and2, or to a surgical tool (15) as schematically shown in FIG. 3.

The invention is described hereinabove by way of non-limiting example.It is clear that the person skilled in the art will be capable ofproducing numerous variants without departing from the scope of theprotection.

I claim:
 1. Apparatus for detecting and locating ionizing-radiationsources retained by a tumor in the environment of a body, comprising:aprobe which can be manipulated by hand, a casing comprising aphotodetector capable of producing a response to an interaction of lightsignals with said photodetector, a signal processor for processingelectrical signals coming from said photodetector to provide drivesignals, and a warning device which responds to said drive signals byemitting an audibly or visually perceptible output signal in response tosaid drive signals which are applied to it, wherein the manipulableprobe comprises at least one scintillating optical fiber cladded with anopaque flexible jacket, and provided with a front end and a rear end,the front end being closed by a plug made of the jacket and the rear endconnecting said probe to said photodetector in order to convert saidlight signals emitted by the scintillating optical fiber into saidelectrical signals.
 2. Apparatus for detecting and locating radiationsources retained by a tumor according to claim 1, wherein the casingcomprises a photomultiplier tube as said photodetector, housed in atubular part and a connection adaptor at the end of said tubular partfor connection of at least one scintillating optical fiber to thephotomultiplier.
 3. Apparatus for detecting and locating radiationsources retained by a tumor according to claim 1, wherein the flexibleopaque jacket is sterilizable and contains a bundle of from 2 to 6scintillating optical fibers having a unitary diameter of approximately1 millimeter.
 4. Apparatus for detecting and locating radiation sourcesretained by a tumor according to claim 2, further comprising a shutterarranged between the photomultiplier and the connection adaptor. 5.Apparatus for detecting and locating radiation sources retained by atumor according to claim 1, wherein the front end of the scintillatingplastic fiber is solidly attached to a functional exploration tool. 6.Apparatus for detecting and locating radiation sources retained by atumor according to claim 1, wherein the front end of the scintillatingplastic fiber is solidly attached to a surgical tool.
 7. Apparatus fordetecting and locating radiation sources retained by a tumor accordingto claim 2, wherein a plug solidly attached to the end of thescintillator fiber is housed in the connection adaptor of the tubularpart, and wherein the tubular part is internally lined with alight-absorbent coating.